Significant advances have been made during the last decade in our ability to diagnose and characterize blood diseases, including inherited disorders, antibody-mediated syndromes, and various acquired thrombo-tic and hemorrhagic risk factors. In addition, an expanding array of therapeutic options is now available for even the rarest of hemostatic disorders. However, because many hemostatic disorders are uncommon, few prospective, randomized clinical trials exist to assess optimal approaches to evaluate and treat these patients. In addition, although millions of patients receive transfusion support annually, few prospective studies are available to guide therapeutic decisions. This is an application from the Division of Hematology at Duke University Medical Center to participate as a Core Clinical Center in the NIH-sponsored Transfusion Medicine/Hemostasis Clinical Research Network. To achieve this, we propose the following aims: (1) Develop and propose multi-center clinical research trials that will accelerate studies in the appropriate use of blood products and novel growth factors, and in the treatment of hemostatic disorders. Clinical trials will be developed by the P.I. and his co-investigators, with protocol review and advice from collaborators and statisticians, for submission to the Network's Steering Committee. We have prepared two clinical research trials for this proposal, one designed to investigate the optimal intensity of anticoagulant therapy in patients with antiphospholipid antibody syndromes, and the second to determine the role of antithrombotic therapy in patients with heparin-induced thrombocytopenia but without evidence for thrombosis. (2) Participate in the Steering Committee and Subcommittees of the Network to ensure appropriate review of proposed studies from individual centers and development of common protocols for implementation. Activities will include organization of the Network, reviewing and finalizing common research protocols, facilitating the conduct and monitoring of all studies, and reporting study results. (3) Work with the Data Coordinating Center and the other Clinical Centers in the Network to efficiently start and complete common clinical research trials at Duke. Implementation of research protocols will include IRB review and approval, regular on-site review of study progress, review of patient recruitment with alternative plans to increase study enrollment as needed, quality control assessments, and reporting of study results.